**5. Conclusions**

An analysis of the unsteady stagnation point flow of hybrid nanofluid over a convectively heated stretching/shrinking sheet incorporating the velocity slip impact on heat transfer was verified in this study. The results were generated by employing the bvp4c features in the MATLAB programming platform. The effect of diverse controlling parameters—namely, the nanoparticle volume fraction, the velocity slip, the Biot number, and the unsteadiness parameter—were reviewed. Our discoveries happen to determine that the presence of non-uniqueness solutions (first and second solutions) is verifiable within the hybrid Al2O3-Cu/H2O nanofluid for a specific range of control parameters, and the stability analysis authorizes the reliability of our first solution. The nanoparticle volume fraction increment improved both the skin friction coefficient and local Nusselt number in the hybrid nanofluid (Al2O3-Cu/H2O). From this, it is proven that the heat transfer rate improves when the ordinary Al2O3-H2O nanofluid becomes the hybrid nanofluid (Al2O3-Cu/H2O) by expanding the nanoparticles concentration. The recent addition of the velocity slip parameter at the boundary had encouraged a reduction in the skin friction coefficient and velocity profile. However, it increased the rate of heat transfer significantly. The temperature profiles escalate as the magnitude of velocity slip upsurge because of such slip may prevent from exchange of total heat in the hybrid nanofluid. An increase in the unsteadiness parameter consequently raises the velocity gradient on the convectively heated stretching/shrinking sheet, thus improving the skin friction coefficient. Besides, an upsurge in the Biot number intensity boosts the heat transfer rate since the Biot number is directly associated with the heat transfer rate coefficient. Thus, it is conversely interrelated to the thermal resistance of the designated problem. Apart from that, the critical values of the different practices of the Biot number imply no significant outcome towards the magnitude of the heat transfer coefficient.

**Author Contributions:** Research design, N.A.Z., R.N., K.N., and I.P.; Formulation and methodology, N.A.Z.; Result analysis, N.A.Z.; Validation, R.N. and K.N.; Article preparation, N.A.Z.; Review and editing, N.A.Z., R.N., K.N., and I.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** The present work is endorsed by the research award (DIP-2017-009) from UKM.

**Acknowledgments:** All authors value the productive feedbacks by the competent reviewers. **Conflicts of Interest:** The authors declare no conflict of interest.
